The term muscle belly refers to the central part of a muscle, or the whole muscle between the tendons. Since the entire muscle, as a unit, is the muscle and the tendons that connect it to the bone, muscle belly is used to differentiate when the central, contracting part of the muscle, containing the myofibrils, is being discussed. An entire skeletal muscle, which is the muscle belly with its tendons, is also referred to as a musculotendinous unit.